JPWO2008132940A1 - Optical information recording medium and manufacturing method thereof - Google Patents

Abstract

Disclosed is an optical information recording medium that is capable of recording at a higher speed and is excellent in mass productivity even when the recording layer of the information layer is thin. In an optical disc 10 that records and reproduces information by changing optical characteristics of a recording layer 14 by laser light irradiation, an oxide protective layer LOx-MOx made of a mixture of an oxide LOx and an oxide MOx is provided. The first interface layer 13 and the second interface layer 15 are stacked adjacent to each other above and below the recording layer 14. Here, the oxide LOx is an oxide of one or more elements selected from lanthanoid elements including Ce, Nd, Eu, Gd, Dy, and the like. The oxide MOx is an oxide of one or more elements selected from Si, Al, and Ta. [Selection] Figure 1

Description

  The present invention relates to an optical information recording medium on which information is optically recorded by irradiation with a laser beam.

  In general, in a rewritable optical disk such as a phase change optical disk, the recording layer is irradiated with laser light, and the recording layer can be used for recording / recording information by changing the optical characteristics such as magneto-optical characteristics, reflectance, and optical phase of the recording layer. Playback is performed. As such an optical disc, DVD-RW and DVD-RAM are generally used, and HD DVD-RAM, HD DVD-RW, and the like are becoming widespread as optical discs capable of further increasing the capacity (Patent Document 1, Non-patent document 1).

  A recording layer of GeSbTe or AgInSbTe is used for the recording layer of the optical disc described above, and an interface layer is provided adjacent to the upper and lower sides of the recording layer in order to promote crystallization of the recording layer and improve repeated recording / reproducing characteristics. The structure is known. As the material for the interface layer, Ge—N, Ge—Cr—N, or the like is generally used.

  In recent years, there has been an increasing demand for further high-speed recording of information and a larger capacity. In order to record the information at high speed, it is necessary to rotate the optical disk at a higher speed than ever before. For example, HD DVD-RAM is desired to operate at 13.2 m / sec, which is twice as fast as the conventional rotational speed of 6.6 m / sec (1 × speed).

  In order to further increase the capacity, for example, an information layer L0 having a first recording layer and an information layer L1 having a second recording layer are sequentially laminated on a single substrate. An optical information recording medium is known. However, since the laser light passes through the information layer L0 and reaches the information layer L1, in order to increase the light transmittance of the information layer L0, the thickness of the recording layer of the information layer L0 is compared with that of a conventional optical information recording medium. It is necessary to make it about half as thin.

JP 2004-213862 A Japanese Journal of Applied Physics Vol.43, No.7B, 2004, pp.4859-4862 "Signal-to-Noise Ratio in a PRML Detection" S.OHKUBO et al

  However, the above technique has the following problems.

  An optical information recording medium having only one information layer has the following film configuration as an example. That is, a first dielectric layer, a lower interface layer, a recording layer, an upper interface layer, a second dielectric layer, and a reflective layer are sequentially laminated on a transparent substrate, and each interface layer has a GeN layer. It is used. Information was recorded on the optical information recording medium having the above configuration by rotating at a linear velocity (13.2 m / sec) twice that of the prior art. As a result, it was confirmed that the recording signal was deteriorated from a stage where the number of repeated recording / reproducing operations was relatively small as compared with the case of recording information at a normal speed (1 × speed: 6.6 m / sec) ( (See FIG. 4 [1]).

In addition, a two-layer optical information recording medium developed for increasing the capacity has the following film configuration as an example. That is, a first information layer formed by sequentially laminating a first dielectric layer, a lower interface layer, a recording layer, an upper interface layer, a second dielectric layer, a metal semi-transmissive layer, and a transmittance adjusting layer on a transparent substrate. And a second information layer is provided thereon via an optical separation layer. Also here, the above-described GeN layer is generally used as the interface layer adjacent to the top and bottom of the recording layer. In addition, ZnS—SiO ₂ is used for the first dielectric layer and the second dielectric layer, and an Ag-based metal semi-transmissive film is used as the metal semi-transmissive layer. Further, as the transmittance adjusting layer, the same ZnS—SiO ₂ or TiO ₂ as that of the first dielectric layer and the second dielectric layer is used. In this case, the thickness of the recording layer of the first information layer is about half that of an optical information recording medium having only one information layer in order to increase the transmittance. However, when the thickness of the recording layer is reduced in this way, the crystallization speed of the recording layer is reduced. For this reason, particularly when performing high-speed recording at a double speed or higher, there is a problem that accurate information cannot be recorded because the crystallization speed of the recording layer is too slow. The reason why the crystallization speed of the recording layer decreases as the recording layer thickness decreases is that crystal nuclei are less likely to occur in the recording layer as the recording layer thickness decreases.

  Further, in order to form the above-described GeN layer, it is essential to introduce nitrogen gas into the film forming gas atmosphere. At this time, when the GeN layer is formed on the recording layer as the upper interface layer, the surface of the recording layer may be nitrided by the nitrogen gas introduced into the chamber. Such a nitridation reaction on the surface of the recording layer is generally irregular, and thus there is a problem that the recording / reproducing characteristics of the optical information recording medium are not constant.

  Accordingly, an object of the present invention has been made in view of such problems, and optical information recording excellent in mass productivity, capable of recording at a higher speed, especially for a thin recording layer. To provide a medium.

  An optical information recording medium according to the present invention is an optical information recording medium comprising a recording layer whose optical characteristics change by irradiation with laser light, and a protective layer laminated on the recording layer, wherein the protective layer Includes a mixture of an oxide LOx of one or more elements selected from lanthanoid elements and an oxide MOx of one or more elements selected from Si, Al, and Ta It is what.

  The method for producing an optical information recording medium according to the present invention is a method for producing an optical information recording medium comprising a recording layer and a protective layer, and after forming the recording layer, the lanthanoid element Using a target including a mixture of an oxide LOx of one or more selected elements and an oxide MOx of one or more selected from Si, Al, and Ta, a rare gas that does not contain oxygen gas is used. The protective layer is formed by sputtering in a gas atmosphere.

  According to the present invention, a mixture of an oxide LOx of one or more elements selected from lanthanoid elements and an oxide MOx of one or more elements selected from Si, Al, and Ta is used. Thus, it is possible to obtain a protective layer that absorbs less laser light and easily generates crystal nuclei in the recording layer. Therefore, it is possible to provide an optical information recording medium in which the recording / reproduction signal is hardly deteriorated even at a high linear velocity or a thin recording layer.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  An optical disc 10 according to Embodiment 1 of the present invention is a rewritable phase change optical disc as shown in FIG. In the optical disk 10, a first dielectric layer 12, a first interface layer 13, a recording layer 14, a second interface layer 15, a second dielectric layer 16, and a metal reflective layer 17 are laminated on a transparent substrate 11 in this order. Yes. The interface layer forms a protective layer in an optical disk (optical information recording medium).

  As the recording layer 14, a general recording material such as GeSbTe or AgInSbTe can be used. In the configuration in which only the first information layer is provided on the substrate, the thickness of the recording layer 14 is desirably about 13 nm to 15 nm in consideration of repeated recording and reproduction operations. The metal reflective layer 17 is preferably made of a material mainly composed of Ag from the viewpoint of achieving both high thermal conductivity and high transmittance. In order to improve weather resistance, an element such as Pd, Cu, Ge, In, or Nd may be added to the material containing Ag as a main component.

The first dielectric layer 12, ZnS-SiO ₂ is generally used. In the composition expression of (ZnS) _x (SiO ₂ ) _1-x , the composition is preferably in the range of 0.5 ≦ x ≦ 0.9 from the viewpoint of refractive index and productivity.

  A GeN layer or the like has been used as the first interface layer 13 and the second interface layer 15. In contrast, in the present embodiment, as the first interface layer 13 and the second interface layer 15, an oxide protective layer LOx-MOx made of a mixture of oxide LOx and oxide MOx is used instead of the GeN layer. Yes. Here, the oxide LOx is an oxide of one or more elements selected from lanthanoid elements such as Ce, Nd, Eu, Gd, and Dy. The oxide MOx is an oxide of one or more elements selected from Si, Al, and Ta. As a result, since the crystallization speed of the recording layer 14 can be increased, it is possible to provide an optical information recording medium with little deterioration of the recording / reproducing signal even at a high linear velocity or even with respect to the thin recording layer 14.

  Lanthanoid elements are relatively easy to bond with oxygen and are very stable once oxide LOx is formed. In addition, the oxide LOx has a very small extinction coefficient and little absorption with respect to a wavelength range of 380 nm to 430 nm of laser light for high density recording. On the other hand, the oxide MOx such as Si, Al, and Ta has excellent adhesion to the recording layer 14. When the oxide LOx and the oxide MOx having such properties are mixed, some kind of synergistic action acts to obtain an interface layer material that absorbs less laser light and easily generates crystal nuclei in the recording layer 14. It is done.

  FIG. 2 is a cross-sectional view showing an optical disc (type A) which is an optical information recording medium according to Embodiment 2 of the present invention. Hereinafter, description will be given based on this drawing. Note that basically the same parts as those in FIG.

  The optical disk 40 of the present embodiment includes a first dielectric layer 12, a first interface layer 13, a recording layer 14, a second interface layer 15, a second dielectric layer 16, a metal semi-transmissive layer 37, on a transparent substrate 11. The third dielectric layer 18 is laminated in this order. Hereinafter, this laminate is referred to as a first information layer 41. Then, the optical separation layer 31 is formed on the first information layer 41, and the second information layer 42 is further disposed thereon. Similar to the first information layer 41, the second information layer 42 is formed on the transparent substrate 21 with the metal reflective layer 22, the third dielectric layer 23, the third interface layer 24, the recording layer 25, the fourth interface layer 26, Four dielectric layers 27 are laminated in this order. The interface layer forms a protective layer in an optical disk (optical information recording medium).

  The first information layer 50 and the second information layer 51 are each laminated on another transparent substrate 11, 21, and finally bonded together via an optical separation layer 31 made of an ultraviolet curable resin. An optical disc 40 having an information layer is obtained. In the optical disc 40, a laser beam used for recording / reproducing information is incident from the first information layer 41 side. Here, the optical disc 40 having such a configuration is referred to as a type A optical information recording medium.

  FIG. 3 is a cross-sectional view showing an optical disc (type B) which is an optical information recording medium according to Embodiment 2 of the present invention. Hereinafter, description will be given based on this drawing. Note that basically the same parts as those in FIG.

  In the present embodiment, a configuration like the optical disc 60 may be used. In the optical disc 60, the metal reflective layer 22, the third dielectric layer 23, the third interface layer 24, the recording layer 25, the fourth interface layer 26, and the fourth dielectric layer are formed on the transparent substrate 21 as the second information layer 42. 27 are laminated in this order, and an optical separation layer 31 made of an ultraviolet curable resin is formed thereon. At this time, a guide groove (not shown) made of lands and grooves is formed on the optical separation layer 31 at the same time, and a third dielectric layer 18, a metal semi-transmissive layer 37, and the like are formed thereon as the first information layer 61. The second dielectric layer 16, the second interface layer 15, the recording layer 14, the first interface layer 13, and the first dielectric layer 12 are laminated in this order, and finally the thickness is about 100 μm using an ultraviolet curable resin. The transparent sheet 51 is adhered. The interface layer forms a protective layer in an optical disk (optical information recording medium).

  In this type of optical information recording medium, laser light used for recording / reproducing information is incident from the first information layer 61 side through the transparent sheet 51. Hereinafter, the optical disc 60 having such a configuration is referred to as a type B optical information recording medium.

  In the type A and type B optical information recording media described above, since the laser light is incident from the first information layer side, the first information viewed from the laser light is different even if the production procedure of each type of medium is different. The stacking order of the layers does not change. Therefore, here, the first information layer of the type A optical information recording medium will be mainly described.

  As the recording layer 14 shown in FIG. 2, a general recording material such as GeSbTe or AgInSbTe can be used. As the metal semi-transmissive layer 37, a material mainly composed of Ag is suitable from the viewpoint of achieving both high thermal conductivity and high transmittance. Elements such as Pd, Cu, Ge, In, and Nd may be appropriately added to the metal semi-transmissive layer 37 in order to improve weather resistance.

The first dielectric layer 12, ZnS-SiO ₂ is generally used. The composition is preferably in the range of 0.5 ≦ x ≦ 0.9 in the composition expression of (ZnS) _x (SiO ₂ ) _1-x from the viewpoint of refractive index and productivity.

  As the first interface layer 13 and the second interface layer 15, a GeN layer or the like has been used. In contrast, in this embodiment, as the first interface layer 13 and the second interface layer 15, an oxide protective layer LOx-MOx made of a mixture of oxide LOx and oxide MOx is used instead of the GeN layer. It was. Here, the oxide LOx is an oxide of at least one element selected from lanthanoid elements (hereinafter referred to as “Group A”) such as Ce, Nd, Eu, Gd, and Dy. The oxide MOx is an oxide of at least one element selected from Si, Al, and Ta (hereinafter referred to as “B group”). Thereby, since the crystallization speed of the recording layer 14 can be increased, it is possible to provide an optical information recording medium in which the recording / reproducing signal is hardly deteriorated even at a high linear velocity or even for the thin recording layer 14.

  In the oxide protective layer LOx-MOx, the content of the oxide LOx selected from Group A is desirably in the range of 35 mol% to 85 mol%. The oxide protective layer LOx-MOx contains Pmol% of the oxide LOx selected from the A group and Q mol% of the oxide MOx selected from the B group, and satisfies 35 ≦ P ≦ 85 and P + Q ≧ 99. It is desirable to form a film by sputtering using an oxide target having a composition in an atmosphere not containing oxygen gas. Here, the reason for setting P + Q ≧ 99 is that less than 1 mol% of a material component such as a crucible is mixed during target fabrication. This “less than 1 mol%” is a numerical value obtained based on past results of target production.

  In the first and second embodiments, the oxide protective layers LOx-MOx are stacked adjacent to the upper and lower sides of the recording layer as the most preferable mode. However, the present invention is not limited to this. For example, the oxide protective layer LOx-MOx may be stacked adjacent to one of the upper and lower sides of the recording layer, and the recording layer may be oxidized with another layer interposed therebetween. An object protective layer LOx-MOx may be stacked.

Next, Example 1 that further embodies Embodiment 1 will be described. In FIG. 1, on a transparent substrate 11, a first dielectric layer 12, a first interface layer 13, a recording layer 14, a second interface layer 15, a second dielectric layer 16, and a metal reflective layer 17 are laminated in this order. The optical disk 10 was manufactured by changing the materials and compositions of the first interface layer 13 and the second interface layer 15 in various ways. ZnS—SiO ₂ was deposited to 50 nm as the first dielectric layer 12, GeSbTe was deposited to 14 nm as the recording layer 14, ZnS—SiO ₂ was deposited to 25 nm as the second dielectric layer 16, and AgPdCu was deposited as the metal reflective layer 17.

Here, a medium using Gd ₂ O ₃ (80 mol%)-SiO ₂ (20 mol%) and a medium using a conventional GeN layer were prepared for the first interface layer 13 and the second interface layer 15, respectively. The medium was rotated at twice the linear velocity of HD DVD-RW (CLV = 13.2 m / sec), and the repeated recording / reproduction characteristics of PRSNR as a performance index were measured.

  The PRSNR (Partial Response Signal to Noise Ratio) is a figure of merit that indicates the signal quality of the optical disk. Specifically, the S / N (signal to noise ratio) of the reproduction signal, the actual reproduction waveform, and the theoretical It is an index that can simultaneously express the linearity of PR waveform, and is used for estimating the bit error rate of an optical disc. Further details are described in, for example, Patent Document 1 and Non-Patent Document 1.

FIG. 4 [1] shows the comparative evaluation results. From FIG. 4 [1], it can be seen that when the Gd ₂ O ₃ —SiO ₂ film is used as the interface layer, the degree of decrease in PRSNR during repeated recording and reproduction is less than that of the medium using the GeN layer. When the GeN layer is used, the PRSNR after repeated recording and reproduction of 10,000 times is 15.4, which barely satisfies the standard value “PRSNR> 15”. As shown in FIG. 4 [2], the difference in these characteristics is that the medium using the Gd ₂ O ₃ —SiO ₂ film as the interface layer has a higher DC erasure rate, so that the crystallization speed of the recording layer is faster. It is because.

  Next, the relationship between the material and composition of LOx and MOx, repeated recording / reproduction characteristics, and storage stability will be described. Here, the repetitive recording / reproducing characteristics indicate a measured value (DOW10K) of PRSNR after 10,000 times of recording / reproducing in the case where the linear velocity of the disk rotation is 13.2 m / sec. Generally, if the PRSNR is 15 or more, the normal recording / reproducing operation is not affected. With respect to storage stability, PRSNR measured values are shown when the same place is measured by conducting an environmental test at a temperature of 80 ° C. and a humidity of 85% for 500 hours with respect to data obtained by repeated recording and reproduction 10 times. The results are shown in FIG.

  From FIG. 5, the PRSNR (DOW10K) after 10,000 recording / reproducing operations decreases as the LOx material content decreases. This is due to the fact that the crystallization rate is slowed with the decrease in the LOx content. Further, the PRSNR after the environmental test shows a good value when the content of the LOx material is in the range of 35 mol% to 85 mol%, but is deteriorated outside this range. If it is less than 35 mol%, it is considered that the crystallization rate is slowed as the LOx content is reduced as described above. On the other hand, when the LOx material exceeds 85 mol%, the content of the MOx material is relatively reduced, so that the affinity for the recording layer is lowered and it is likely that the material is easily peeled off.

  Next, Example 2 that further embodies the second embodiment will be described. In FIG. 2, the optical disc 40 is provided with a transparent substrate 11 on which a first dielectric layer 12, a first interface layer 13, a recording layer 14, a second interface layer 15, and a second dielectric material are provided. The layer 16, the metal semi-transmissive layer 37, and the third dielectric layer 18 are laminated in this order. This stacked body is the first information layer 41. Then, the optical separation layer 31 is formed on the first information layer 41, and the second information layer 42 is further disposed thereon. Similar to the first information layer 41, the second information layer 42 is formed on the transparent substrate 21 with the metal reflective layer 22, the third dielectric layer 23, the third interface layer 24, the recording layer 25, the fourth interface layer 26, The fourth dielectric layer 27 is laminated in this order. The first information layer 41 and the second information layer 42 are laminated on different transparent substrates 11 and 21, respectively, and finally bonded to each other via an optical separation layer 31 made of an ultraviolet curable resin. The optical disc 40 having 41 and 42 is obtained. In the optical disc 40, a laser beam used for recording / reproducing information is incident from the first information layer 41 side. Therefore, this is a type A optical information recording medium.

  In the present embodiment, only the first information layer 41 is manufactured and a dummy substrate is bonded to the first information layer 41, and the results of examination are described. Regarding the second information layer 42, the medium configuration described in the first embodiment is simply laminated in reverse, and therefore material selection based on the first embodiment may be performed.

The first information layer 41 includes ZnS-SiO ₂ of 50 nm, 17 nm, and 110 nm as the first dielectric layer 12, the second dielectric layer 16, and the third dielectric layer 18, and 7 nm of GeSbTe as the recording layer 14. As the transmissive layer layer 37, AgPdCu was formed to a thickness of 10 nm.

Here, as the first interface layer 13 and the second interface layer 15, and select the _Gd 2 _{O 3} and _Eu 2 _{O 3} from the LOx, _Gd 2 _O 3, which selects the SiO ₂ from the MOx (40 mol%) _{-Eu 2 O 3 (40mol%)} - were prepared SiO 2 (20mol%) layer medium was used, and a medium using a conventional GeN layer. Each medium was rotated at a double linear velocity equivalent to HD DVD-RW (CLV = 13.2 m / sec), and repeated recording / reproduction characteristics of PRSNR as a performance index were measured. The thickness of each interface layer is 5 nm.

FIG. 6 [1] shows the comparative evaluation results. As shown in FIG. 6 [1], when the Gd ₂ O ₃ —Eu ₂ O ₃ —SiO ₂ layer is used, the degree of decrease in PRSNR during repetitive recording / reproduction is much smaller than that of a medium using a GeN layer. Recognize. On the other hand, when the GeN layer is used, the PRSNR after 10,000 repetitive recording / reproducing operations is 7 and the PRSNR at the first 11 repetitive recording / reproducing operations is 12.8, which is a low value outside the standard value. ing. This is because, as shown in FIG. 7 [2], when the film thickness of the recording layer is as thin as 7 nm, the crystallization speed is low under a high linear velocity even when the GeN layer is used. On the other hand, when the Gd ₂ O ₃ —Eu ₂ O ₃ —SiO ₂ layer is used, since the DC erasure rate is lower than when the recording layer is thick (FIG. 4 [2]), the crystallization speed is slightly reduced. However, the PRSNR never falls below 15, and the recording / reproducing operation can be performed without any problem.

  Next, the relationship between the material and composition of LOx and MOx, repeated recording / reproduction characteristics, and storage stability will be described. Here, the repetitive recording / reproducing characteristics indicate PRSNR (DOW10K) after 10,000 times of recording / reproducing when the linear velocity of the disk rotation is 13.2 m / sec. Generally, if the PRSNR is 15 or more, the normal recording / reproducing operation is not affected. With respect to storage stability, PRSNR is shown when data obtained after repeated recording and reproduction 10 times are subjected to an environmental test at a temperature of 80 ° C., a humidity of 85%, and 500 hours, and the same location is measured. The results are shown in FIGS.

7 and 8, (1) Gd ₂ O ₃ -Eu ₂ O ₃ —SiO ₂ layer in which Gd ₂ O ₃ and Eu ₂ O ₃ are selected as LOx and SiO ₂ is selected as MOx, (2) LOx CeO ₂ and Nd ₂ O ₃ are selected as the CeO ₂ -Nd ₂ O ₃ -Ta ₂ O ₅ layer selected as the MOx and Ta ₂ O ₅ is selected as the MOx, and (3) Gd ₂ O ₃ and Dy ₂ O ₃ are selected as the LOx. If the selected, one of _{Gd 2 O 3 -Dy 2 O 3} -Al 2 O 3 layers was chosen for _Al 2 _{O 3} MOx, was used as the interface layer positioned adjacent to and below the recording layer, The measured value (DOW10K) of PRSNR after 10,000 times of recording / reproducing decreases as the content of the LOx material decreases. This is due to the fact that the crystallization speed becomes slower as the LOx content decreases.

  Further, the PRSNR after the environmental test shows a good value when the content of the LOx material is in the range of 35 mol% to 85 mol%, but is deteriorated outside this range. If it is less than 35 mol%, it is thought that as described above, the crystallization rate becomes slower as the content of LOx decreases. On the other hand, when the LOx material exceeds 85 mol%, the content of the MOx material is relatively reduced, so that the affinity for the recording layer is lowered and it is likely that the material is easily peeled off.

From the experimental results shown in FIG. 7 and FIG. 8, the parameter that determines the characteristics of the medium is the mixing ratio of the LOx and MOx materials, and is selected from the LOx even if a plurality of materials are mixed in the LOx. It was experimentally confirmed that good characteristics can be obtained when the ratio of the material is in the range of 35 mol% to 85 mol%. In the combination of Gd ₂ O ₃ -Eu ₂ O ₃ and Gd ₂ O ₃ -Dy ₂ O ₃ among the combinations of LOx materials, recording is performed as the ratio of Eu ₂ O ₃ and Dy ₂ O ₃ increases. A tendency to increase sensitivity was also confirmed at the same time.

Next, Example 3 that further embodies the first embodiment will be described. In FIG. 1, on a transparent substrate 11, a first dielectric layer 12, a first interface layer 13, a recording layer 14, a second interface layer 15, a second dielectric layer 16, and a metal reflective layer 17 are laminated in this order. The optical disk 10 was manufactured by changing the materials and compositions of the first interface layer 13 and the second interface layer 15 in various ways. ZnS—SiO ₂ was deposited to 50 nm as the first dielectric layer 12, GeSbTe was deposited to 14 nm as the recording layer 14, ZnS—SiO ₂ was deposited to 25 nm as the second dielectric layer 16, and AgPdCu was deposited as the metal reflective layer 17.

Here, 500 media each using a Gd ₂ O ₃ (80 mol%)-SiO ₂ (20 mol%) layer and a GeN layer for the first interface layer 13 and the second interface layer 15 were prepared. did. Next, these media were rotated at a double linear velocity of HD DVD-RW (CLV = 13.2 m / sec), PRSNR as a performance index was measured, and the fluctuation range of PRSNR was compared.

FIG. 9 shows the measurement results of PRSNR when each interface layer is used. From FIG. 9, it can be seen that the variation in the measured value of PRSNR is larger in the GeN layer. This is because when a GeN layer is formed, reactive film formation is performed in a mixed gas atmosphere of Ar gas and nitrogen gas, so that Ar and nitrogen gas are introduced into the sputtering chamber when the second interface layer 15 is formed. Since the surface of the recording layer 14 previously formed is nitrided, it seems that the fluctuation of PRSNR becomes large. Therefore, if a Gd ₂ O ₃ —SiO ₂ layer or the like that does not require introduction of nitrogen gas or oxygen gas and can be formed only with Ar gas, the PRSNR fluctuates without worrying about nitridation on the surface of the recording layer. There is nothing.

  In addition to Examples 1 to 3 described above, the same effect can be obtained when the first interface layer 13 and the second interface layer 15 are made of a combination of materials selected from the aforementioned group A and group B. Has been confirmed to be obtained. The measurement results of the recording / reproducing characteristics of Examples 1 to 3 described above are in the laser wavelength range of 380 nm to 430 nm.

  An embodiment of the present invention is an optical information recording medium comprising a recording layer whose optical characteristics are changed by laser light irradiation, and a protective layer laminated on the recording layer, the protective layer comprising a lanthanoid-based recording medium A mixture of an oxide LOx of one or more elements selected from elements and an oxide MOx of one or more elements selected from Si, Al, and Ta is included.

  The lanthanoid elements have properties similar to each other, are relatively easily bonded to oxygen, and become very stable once the oxide LOx is formed. Further, the oxide LOx has a very small extinction coefficient at the wavelength of the laser beam for high-density recording and little absorption. On the other hand, oxides MOx such as Si, Al, and Ta have excellent adhesion to the recording layer. When the oxide LOx and the oxide MOx having such properties are mixed, it is considered that some kind of synergistic action acts to form an interface layer material that has little optical absorption and easily generates crystal nuclei in the recording layer. It is done. Therefore, the optical information recording medium according to the embodiment of the present invention has an effect that the deterioration of the recording / reproducing signal is small even at a high linear velocity or a thin recording layer.

  Moreover, it is good also as content of the said oxide LOx in the said protective layer being in the range of 35 [mol%]-85 [mol%]. The lanthanoid element may be Ce, Nd, Eu, Gd, and Dy. The protective layer is preferably stacked adjacent to at least one of the upper and lower sides of the recording layer, and more preferably stacked adjacent to the upper and lower sides of the recording layer. In these cases, the above-mentioned effect appears more remarkably.

  Furthermore, the wavelength of the laser light may be 380 [nm] to 430 [nm]. At this time, the extinction coefficient of the oxide LOx with respect to the laser light becomes extremely small.

  Furthermore, the recording layer is composed of two layers, a first recording layer and a second recording layer, and the second recording layer is irradiated with the laser light transmitted through the first recording layer, and at least the first recording layer The protective layer may be stacked adjacent to the upper and lower layers. At this time, since the first recording layer has to be thinned in order to increase the light transmittance, the above-described effect appears more remarkably.

  In the method for manufacturing an optical information recording medium according to an embodiment of the present invention, the protective layer is formed in the rare gas atmosphere containing no oxygen gas using the target composed of the mixture after forming the recording layer. The film is formed by sputtering. In this case, when a protective layer is formed on the recording layer, no oxidation reaction or nitridation reaction occurs on the recording layer surface. The target may include P [mol%] of the oxide LOx and Q [mol%] of the oxide MOx and have a composition satisfying 35 ≦ P ≦ 85 and P + Q ≧ 99. In this case, the above-mentioned effect appears more remarkably.

  In other words, the optical information recording medium according to the embodiment of the present invention is an optical information recording medium having a recording layer and a protective layer for recording and reproducing information by changing optical characteristics of the recording layer by laser light irradiation. The oxide protective layer LOx-MOx made of a mixture of the oxide LOx and the oxide MOx is laminated adjacent to the upper and lower sides of the recording layer. Here, the oxide LOx is an oxide of at least one element selected from lanthanoid elements such as Ce, Nd, Eu, Gd, and Dy. The oxide MOx is an oxide of at least one element selected from elements such as Si, Al, and Ta. The optical information recording medium according to the present invention is characterized in that the oxide protective layer has a content of oxide LOx in the range of 35 mol% to 85 mol%. In addition, the manufacturing method according to the embodiment of the present invention includes the oxide protective layer included in the optical information recording medium that records and reproduces information by changing the optical characteristics of the recording layer by laser light irradiation. Is formed by sputtering in a rare gas atmosphere not containing oxygen gas, using an oxide target having a composition satisfying 35 ≦ P ≦ 85 and P + Q ≧ 99, including Pmol% and oxide MOx Qmol%. Features. In the optical information recording medium according to the embodiment of the present invention, information is recorded / reproduced using a semiconductor laser having a wavelength of 380 nm to 430 nm.

  As described above, in the embodiment of the present invention, as the interface layer arranged adjacent to the upper and lower sides of the recording layer, the oxide protection composed of the mixture of the oxide LOx and the oxide MOx is used instead of the above-described GeN layer. Layers LOx-MOx are used. Here, the oxide LOx is an oxide of at least one element selected from lanthanoid elements such as Ce, Nd, Eu, Gd, and Dy. The oxide MOx is an oxide of at least one element selected from Si, Al, and Ta. Thereby, since the crystallization speed of the recording layer can be increased, it is possible to provide an optical information recording medium in which the recording / reproducing signal is hardly deteriorated even at a high linear velocity or for a thin recording layer. .

While the present invention has been described with reference to the embodiments (and examples), the present invention is not limited to the above embodiments (and examples). Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2007-109040 for which it applied on April 18, 2007, and takes in those the indications of all here.

1 is a cross-sectional view showing an optical disc as a first embodiment of an optical information recording medium according to the present invention. It is sectional drawing which shows the optical disk (type A) as 2nd embodiment of the optical information recording medium based on this invention. It is sectional drawing which shows the optical disk (type B) as 2nd embodiment of the optical information recording medium based on this invention. FIG. 4 [1] is a graph comparing the repeated O / W resistance of each medium in Example 1, and FIG. 4 [2] compares the linear speed dependence of the DC erasure rate of each medium in Example 1. It is a graph. 6 is a chart showing evaluation results of media using various interface layers in Example 1. FIG. 6 [1] is a graph comparing the repeated O / W resistance of each medium in Example 2, and FIG. 6 [2] compares the linear velocity dependence of the DC erasure rate of each medium in Example 2. It is a graph. 6 is a chart showing evaluation results (part 1) of a medium using various interface layers in Example 2. It is a chart which shows the evaluation result (the 2) of the medium using the various interface layers in Example 2. 10 is a chart showing a relationship between a gas atmosphere and PRSNR at the time of forming an interface layer in Example 3.

Explanation of symbols

10 Optical disc (optical information recording medium)
11 Transparent substrate 12 First dielectric layer 13 First interface layer (protective layer)
14 Recording layer (first recording layer)
15 Second interface layer (protective layer)
16 Second dielectric layer 17 Metal reflective layer 18 Third dielectric layer 21 Transparent substrate 22 Metal reflective layer 23 Third dielectric layer 24 Third interface layer (protective layer)
25 Recording layer (second recording layer)
26 Fourth interface layer (protective layer)
27 Fourth dielectric layer 31 Optical separation layer 37 Metal semi-transmissive layer 40 Optical disc (optical information recording medium)
41 First Information Layer 42 Second Information Layer 51 Transparent Sheet 60 Optical Disc (Optical Information Recording Medium)
61 First information layer

Claims (9)

In an optical information recording medium comprising a recording layer whose optical characteristics are changed by laser light irradiation, and a protective layer laminated on the recording layer,
The protective layer includes a mixture of an oxide LOx of one or more elements selected from lanthanoid elements and an oxide MOx of one or more elements selected from Si, Al, and Ta. An optical information recording medium.   2. The optical information recording medium according to claim 1, wherein the content of the oxide LOx in the protective layer is in a range of 35 [mol%] to 85 [mol%].   The optical information recording medium according to claim 1, wherein the lanthanoid element is Ce, Nd, Eu, Gd, and Dy.   The optical information recording medium according to claim 1, wherein the protective layer is laminated adjacent to at least one of upper and lower sides of the recording layer.   The optical information recording medium according to claim 1, wherein the protective layer is laminated adjacent to the top and bottom of the recording layer.   The optical information recording medium according to claim 1, wherein a wavelength of the laser light is 380 [nm] to 430 [nm].   The recording layer is composed of two layers, a first recording layer and a second recording layer, and the second recording layer is irradiated with the laser light transmitted through the first recording layer, and at least above and below the first recording layer. The optical information recording medium according to claim 1, wherein the protective layer is laminated adjacent to the optical information recording medium. A method for producing an optical information recording medium comprising a recording layer and a protective layer,
After forming the recording layer, an oxide LOx of one or more elements selected from lanthanoid elements, and an oxide MOx of one or more elements selected from Si, Al, and Ta A method for producing an optical information recording medium, wherein the protective layer is formed by sputtering in a rare gas atmosphere not containing oxygen gas, using a target containing a mixture of the above.   9. The target according to claim 8, wherein the target includes a composition that includes P [mol%] of the oxide LOx and Q [mol%] of the oxide MOx, and satisfies 35 ≦ P ≦ 85 and P + Q ≧ 99. Manufacturing method of optical information recording medium.

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